(1) Field of the Invention
The present invention relates to security of document data and especially to a technique of restricting usage locations of document data.
(2) Description of the Related Art
In recent years, business and government entities are facing the growing problem of leakage of confidential information as a result of, for example, careless handling. It is a must that each and every individual pays due attention. Yet, it is not sufficient to provide adequate security and various security measures have been suggested.
For example, one known system permits a user to make a data access to a server computer, on condition that the user is physically within a predetermined location (See JP Patent Application Publication No. 6-138969). In another known system, a terminal is provided with GPS to detect a current location of the terminal. The terminal, is permitted to use content data received from a server computer, on condition that the current location coincides with a predetermined location indicated by information stored on a memory card (JP Patent Application Publication No. 2005-56204). In yet another known system, a server computer grants an access right to a terminal based on the physical location of the terminal. The terminal is enabled to decrypt an electronic file only if the access right has been granted (JP Patent Application Publication No. 2006-72808).
Unfortunately, however, the above techniques known in the art have the following disadvantages. Although the above techniques achieve to protect data by restricting locations within which the data is permitted to be used, a costly special-purpose terminal needs to be provided and used to access the data. Thus, users of the system is forced to use a general-purpose terminal for routine work and to use the special-purpose terminal when accessing the protected data, which leads to workflow complication and inefficiency. It may be true that provision of costly special-purpose terminals to each and every user eliminates the complication. However, such a measure is impractical in view of high costs expected to be incurred.
In addition, the above prior art relates to security of data stored, for example, on a server computer. That is, no security is provided for data that is expected to be transferred out of a predetermined location and thus there is a need for such a new technique.